Ko Youngkil

 Biological Evidence  5 prediction  compare with experimental results  Primary visual cortex (V1) is involved in image segmentation, but it works with higher-order.

 Primary visual cortex is involved in image segmentation  Predictions of the weak-membrane model for segmentation  Two distinct groups of neurons, one set coding region properties, the other set codes boundary location  The processes for computing the region and the boundary are tightly coupled  The regional properties diffuse within each region and tend to become constant  The interruption of the spreading of regional information by boundaries results in sharp discontinuities in the responses across two different regions  In the continuation method, there is additional sharpening of the boundary response.

 Conjecture that segmentation computation is embodied in V1.  Not all the computations required for segmentation need take place in V1  Surface inference takes place in V2, but the process can be coupled to the segmentation process in V1 through recurrent connections.  High-resolution buffer theory  V1 acts as a high-resolution computational buffer which is involved in all visual computations that require high spatial precision and fine-scale detail.  Segmentation in V1 cannot be complete and robust without integrating with other high-order computation.  Experiments  The gradual sharpening of the response to boundaries  The simultaneous spreading of regional properties  The development of abrupt discontinuities in surface representations across surfaces.

 Gabor filter  They can be derived from the statistics of natural images as efficient codes for natural images based on independent component analysis  The odd-symmetric Gabors are sensitive to intensity edges and the even-symmetric Gabors to bars (such as peaks and valleys).  Simple cells can serve as edge and bar detectors  The complex cells, which are not sensitive to the polarity of the luminance contrast at edge, would be particularly suitable for representing borders or boundaries of regions.  The Hypercomplex cells could serve as derivative operators which act on complex cells’ responses to detect texture boundaries

Half-height width of the spatial response profile around the boundary decrease overtime  consistent with the boundary- sharpening prediction. V1 is still needed to represent the residual information between the high- level prediction and the image stimulus.

 V1 neurons respond much more strongly when their receptive fields are inside the figure than when they are in the background.  This enhancement was uniform within the figure and terminated abruptly at boundary  Classical iso-orientation surround suppression theory ▪ A uniform enhancement within the figure ▪ Abrupt discontinuity of enhancement response at the border

 The enhancement was found to decrease as the size of the figure increased.  Responded primarily to the boundaries  Responded well inside the figure  Boundaries and inside the surface.  Prediction 1, some neurons responded more to the color regions, others responded more to the boundaries.

 Precise “coloring” of the figure to highlight it for further processing.  Process of target selection and the process of segmentation might be tightly coupled:  Segmentation constrains the target enhancement, but segmentation itself also depends on target selection.